Democratic presidential candidate Hillary Clinton leads Republican Donald Trump by 5 percentage points, according to a Reuters/Ipsos tracking poll released on Friday, keeping her advantage in a national survey while races tighten in several swing states.

The Oct. 30-Nov. 3 opinion poll showed that 44 percent of likely voters in Tuesday's election support Clinton while 39 percent support Trump.

Reuters/Ipsos

Clinton

44%

Trump

39%

Clinton's lead has varied from 4 to 7 percentage points every day over the past week in the Reuters/Ipsos poll, while other opinion polls have shown the race becoming increasingly competitive. Real Clear Politics, which averages together most national polls, estimates that Clinton's lead has dropped from 5 points at the end of last week to less than 2 points on Friday.

The Reuters/Ipsos States of the Nation project shows races in Florida, North Carolina and Michigan have tilted away from Clinton over the past week and are now considered too close to call. These swing states are hotly contested because their voters can swing either to Republicans or Democrats and can be decisive in presidential elections.

Fox News

Clinton

45%

Trump

43%

The project estimates that Clinton still has a 90 percent chance of winning the election, however.

With four days before Election Day, Republicans are increasingly optimistic about Trump winning.